The present invention relates to exercise apparatus such as used for weight lifting, for body building, or for physical therapy and rehabilitation purposes.
Exercise apparatus of this sort frequently includes weights which are lifted or moved in such a way as to stress the user's muscles and thus to aid in developing or maintaining muscle strength, tone and quality. Familiar examples include so-called free weights--dumbbells and barbells--and weight machines including so-called machine stack weights. Such apparatus is found in health clubs and gymnasiums for maintaining health and fitness and in physical therapy and rehabilitation centers for those recovering from injury.
Most such weights may only be varied in predetermined increments. Free weights are typically stored on racks, which hold a variety of smaller weights which serve as building blocks to build up the total weight desired to be lifted or which may hold a separate barbell or dumbbell for each total weight. In any event the weight to be lifted may be varied only in fixed increments of typically five or ten pounds. The weights of the "machine stack weight" type of apparatus are built into the apparatus and similarly may only be varied in fixed increments of ten pounds. Thus a deficiency in such exercise apparatus is that the user has limited ability to adjust the increment with which the weight may be increased or decreased. Manufacturers have been unwilling in the past to supply weights in smaller and smaller increments undoubtedly for a variety of reasons. The cost of the additional apparatus would strain the budgets of typical health clubs or exercise facilities, or it would take too much space to store the additional weights or incorporate them into the stacks of the machine stack weights, or in some cases a small incremental weight, such as a fraction of a pound, may not be able to be incorporated into the apparatus with sufficient structural integrity for reliable and safe use.
A disadvantage of known weight apparatus is that users may experience excessive strain and be subject to injury because they must increase the weights in too great an increment. For example, progressing from a fifteen pound pair of dumbbells to a twenty pound pair represents a 33% increase in workload. For some users, particularly those in physical therapy trying to recover from injury, a 33% step may be too large, but this is all that is possible with the readily available equipment.
U. S. Pat. Nos. 3,758,109, 4,453,710, 4,531,728 and 4,712,793 disclose exercise equipment having auxiliary weights to permit gradual increase in the aggregate weight being lifted. The auxiliary weights of these patents, however, are useful only with the specific equipment for which they were designed. Such specialized auxiliary weights are not practical for most exercise facilities precisely because they are limited to use with the one piece of apparatus. While it might be cost effective to buy one set of auxiliary weights to be used with all apparatus, it generally will not be cost effective to buy separate sets of auxiliary weights to be used with each difference piece of apparatus in the exercise facility.